


The Power of Three

by tabbytabbytabby



Category: Merlin (TV), Teen Wolf (TV)
Genre: Arthur Pendragon Returns, Derek Hale Is Arthur Pendragon, Developing Relationship, Feels, First Kiss, Fluff, Idiots in Love, Light Angst, Love Confessions, M/M, Married Derek Hale/Theo Raeken, Memories, Polyamory, Reincarnation
Language: English
Status: Completed
Published: 2018-07-08
Updated: 2018-07-08
Packaged: 2019-06-07 00:58:44
Rating: General Audiences
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 2,739
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/15207338
Author URL: https://archiveofourown.org/users/tabbytabbytabby/pseuds/tabbytabbytabby
Summary: Derek is happily married to Theo. The two have a good life together. Then he meets a man at the park that introduces himself at Merlin and his world goes spinning on its axis as memories of a life long since forgotten come flooding back to him. Suddenly he's not just Derek but also Arthur. He's afraid of having to choose between his two lives, but Theo has an interesting solution.





	The Power of Three

**Author's Note:**

> I honestly don't know what this is, or how to tag this. I was watching Humans and just kept thinking about how soft Colin looked. And then that led to me wanting Merlin/Derek/Theo. Which with me meant a spiral.

Derek watches him. He can’t help it. There’s something familiar about him, or maybe just the look in his eyes. It’s the same look he saw every time he looked in the mirror after the fire happened. The look of loss and despair, guilt and loneliness. It took him a long time to get past all that, to finally let himself move on and be happy. Something tells him this man has been feeling this way for longer than Derek can even imagine and it makes him sad. No one should feel that way.

“You’re staring again,” Theo says, taking a seat next to him on the bench.

“I can’t help it,” Derek says, letting his eyes move from the man over to Theo. “He looks lonely, and sad. And I just…”

“It reminds you of how you felt,” Theo says, nodding his head. “Yeah I figured. And I get it. But staring at him isn’t going to help anything Der.”

“You’re right,” Derek says, getting to his feet abruptly. “I need to talk to him.”

“Seriously?”

“Yeah, I need to find out his name at least. And see if I can do anything for him,” Derek says.

“Derek you know as well as I do that when someone is hurting that much they’re not always open to talking or accepting help,” Theo says.

“I know that, but I at least have to try.”

“Of course you do,” Theo smiles, “Good luck.”

Derek walks forward slowly, each step feeling like it’s bringing towards something big. He can feel his heart thudding in his chest and his palms getting sweaty. He stops short when the man looks at him, his blue eyes full of surprise, as if he hadn’t expected to see Derek there.

“Can I help you?” The man asks, his voice sending a jolt through Derek.

“I was hoping I could talk to you,” Derek says.

“Why?” the man asks, tilting his head as he studies Derek.

“I’ve seen you here a lot,” Derek tells him. “And I can’t explain it but something keeps pulling me towards you, which I know probably sounds crazy and creepy and I’m sorry if it freaks you out. I just needed to come over here.”

The man’s eyes search his face before he nods, gesturing to the spot on the ground next to him. Once Derek is sitting he holds out his hand, “I’m Merlin.”

“Derek,” he puts his hand in Merlin’s and sucks in a breath, his world turning on his axis. He falls back, barely able to register both Theo and Merlin’s concerned voices. His mind is flooded, memories from a time long since passed rushing into him. A kingdom and people and a love long since forgotten. He lays there, eyes on the sky as he tries to get his breathing under control.

“Merlin,” Derek breathes, his eyes moving over to meet Merlin’s. “ _Merlin._ ” Derek can see the hesitation in Merlin’s eyes as he looks at him, and Derek understands then, “You’ve been coming here for me, haven’t you? You’ve known I’m him all this time.”

“Derek what are you talking about?” Theo asks, bringing a hand up to Derek’s head, “Are you alright? Did you hit your head too hard?”

Derek shakes his head, “No, I just… I remembered.”

“Remembered what” Theo asks, confusion clear in his voice.

“Who I am,” Derek says.

Theo’s lips tilt up into a worried smile, “What do you mean who you are? You’re Derek Hale, my husband.”

Derek nods, “Yes, but I’m also Arthur Pendragon, King of Camelot.”

“God you really did hit your head,” Theo whispers.

“He didn’t,” Merlin says, looking at Derek in awe, “You really remember?”

Derek nods, sitting up. “I do. And I’m so sorry Merlin. I’m sorry you’ve had to wait all this time for me and that it took me so long to find my way back to you.”

Merlin shakes his head, his eyes swimming with tears, “You were always worth the wait Arthur.”

Derek moves forward, pulling Merlin in for a tight hug. He’s spilling tears of his own by now. Merlin grips him tightly, as if he’s afraid Derek, no _Arthur_ , is going to just disappear, “I missed you so much Arthur.”

“I know, Merlin,” Derek says, “but I’m here now. And umm…”

“What is it?”

“I know you know me as Arthur, and I know that’s who I was or who I am, but in this life I go by Derek.”

Merlin nods, his eyes dancing with a familiar amusement. “Okay _Derek_.”

Derek’s only a little surprised when Merlin leans in and kisses him, soft and chaste. It feels like a long time coming.

“Excuse me?” Theo’s shocked voice brings Derek back to where he is, as he pulls away to look at his husband, “What the hell is this?”

Derek looks from Theo back to Merlin, who gives him a sad smile. “It’s okay Derek. I know you have a life now. I just… I never took a chance on that back in Camelot and I spent centuries regretting it. I wouldn’t have been able to live with myself if I let you go without doing what I’ve been dreaming about for 1500 years.”

Derek nods, giving Merlin a small smile. He can understand that. But he knows right now Theo doesn’t. Derek feels torn between two worlds. The one he had with Merlin all those years ago and the one he has now with Theo. He knows he owes Theo a proper explanation for everything and all he can do is hope he’ll understand and believe him. It might be selfish but he doesn’t want to lose either of them.

He turns to Theo, “I’m going to explain everything when we get home, I promise. Can you just give me a moment?”

Theo looks conflicted but nods, placing a kiss to Derek’s cheek before standing up. Derek watches as he walks away, looking back every few feet. When Theo is far enough away he turns to Merlin to see him watching him.

“You love him,” Merlin says.

“I do,” Derek nods, “He’s… well up until now I thought he was the love of my life. We’ve been through so much and he’s made me happier than I ever thought I could be after everything I went through.”

“It’s okay Derek,” Merlin says, giving him an understanding smile, “I get it. I’ve fallen in love a lot over the centuries, all the while loving you. I know better than anyone that it’s possible to love more than one person.”

“I don’t want to lose him,” Derek says, his voice soft, “or you.”

“Then talk to him,” Merlin says, “Explain to him the best way that you can. I can tell he wants to believe you, otherwise he wouldn’t have left you here so easily.”

Derek looks over at where Theo is standing, his back against a tree and his eyes on the sky. Derek appreciates that he’s trying to give them as much privacy as he can. He turns back to Merlin, “I should go.”

Merlin nods, getting to his feet at the same time Derek does. Derek pulls out his phone and hands it to Merlin, “Can I get your number? Assuming you have a phone…”

Merlin rolls his eyes and takes Derek’s phone, “Of course I have a phone Derek. I’m not that big of a recluse. Not like you when you went off the grid a few years back.”

“Wait, you knew?”

Merlin gives him a sheepish smile, handing Derek’s phone back to him. “Yeah I knew. I just wanted to give you space. I wasn’t sure if you’d remember on your own or what the protocol was and your life seemed messy enough. I didn’t want to add to it.”

“Were you there the whole time?”

Merlin shakes his head, “No I gave you space. Granted when I heard about some of the things that you went through I wish I’d stayed.”

“It’s probably better you didn’t,” Derek says. He glances at Theo to see his eyes now on Derek and Merlin and sighs, “I need to go.”

“You do,” Merlin agrees. “Just be as honest as you can Derek. He loves you. I know he’ll come around. I’ll see you.”

With that he waves and walks off, giving Derek a smile before disappearing around the corner. Derek turns and walks towards Theo, who doesn’t say anything when Derek reaches him. He just starts towards the car, leaving Derek to follow. He doesn’t say anything the whole drive home either or when they get to the house. He goes straight to their room.

Derek follows him, confusion and worry building in him when he gets to the room and sees Theo has a bag open on the bed as he pulls clothes from their dresser. “Theo? What on earth are you doing?”

“I’m packing,” Theo says, without even bothering to turn around.

“I can see that, but why?”

Theo stills, his shoulders slumping, “I believe you.”

Derek momentarily feels relieved that he won’t have to explain everything to Theo and hope he understands. Then he watches as Theo continues to put clothes into his bag. “That doesn’t explain why you’re packing,” Derek says, taking a step closer to his husband.

Theo lets out a wet laugh as he shakes his head and turns to Derek, one of his shirts balled up in his hand, “You’re Arthur. You’re _the_ Arthur. And you clearly have a history with Merlin. I could see that. Hell I know that. I’m more than aware of the legends. Then there’s the way you two looked at each other… On top of that, he waited over a thousand years for you. I can’t compete with that Derek.”

“I’m not asking you to,” Derek says, reaching out for Theo who immediately backs away, “Theo please just… I love _you_. You’re my husband. The man I married and vowed to spend the rest of my life with. That hasn’t changed.”

“But you love him,” Theo whispers.

“It is possible to love two people at once,” Derek says, repeating Merlin’s words. “Unless… you want me to choose?”

His heart thuds in his chest as he leans against the wall and slides down it. Breathing becomes hard as his vision blurs. He meant what he told Merlin, he doesn’t want to lose either of them. Now he might and he’s not sure what he can do to stop it.

“Derek,” Theo says, his voice soft as he kneels in front of him.

“I can’t lose you Theo,” Derek says, his voice thick with unshed tears. “I can’t. But I can’t lose him either. I just got him back. I…”

“I know,” Theo sighs, resting his forehead against Derek’s, “I think we’ve been through a lot tonight. Maybe we should get some sleep.”

“You’ll stay?” Derek asks, looking up at Theo.

Theo nods, giving him a small smile, “Yeah Der. I’ll stay.”

Derek surges forward, wrapping Theo up in a tight hug, “I love you.”

“I love you too, Der,” Theo murmurs, “So much.”

Derek stands on shaky legs and gets changed, his eyes on Theo as he does the same. He crawls into bed and holds out his hand to Theo, who takes it with only a second’s hesitation. He tries to tell himself it means something that Theo has decided to stay.

“I don’t want to lose you either,” Theo mumbles, “We’re going to get through this.”

**3 Years Later**

“Derek have you seen my phone?” Merlin calls from the living room.

Derek takes the toothbrush out of his mouth and spits, preparing to answer Merlin, but Theo beats him to it, “In the bedroom!”

Derek finishes brushing his teeth and walks out of the bathroom to see Theo holding Merlin’s phone out to see. Merlin gives him a grateful smile and takes it before leaning up to kiss Theo on the cheek. “Thanks.”

Theo just shakes his head, an answering smile forming on his lips. “Someone has to keep track of where you both leave your stuff. You two certainly don’t.”

“Hey!” Derek says, faking offense as he walks up to the pair, “I can keep track of my things.”

Merlin snorts, “Sure you can.”

Theo ruffles his hair and places a soft kiss on his lips, “You’re worse than Merlin is.”

“He always has been bad about remembering where he puts things,” Merlin grins. “Though you are a little better now than you were back then. In Camelot you were hopeless.”

“Maybe I just liked having an excuse to have you around,” Derek says, leaning in to place a kiss to Merlin’s lips.

Merlin returns the kiss, hooking his arms around Derek’s waist. “Sure you did, at first. Then you just became reliant on me. Face it, you would have been lost without me.”

Derek just nods, “I would have.”

“Breakfast is ready!” Theo calls from the kitchen, “So you two better come get it while it’s hot. I’m not about to hear you complaining about cold eggs just because you couldn’t stop kissing for 5 minutes.”

“I believe last time you were just as guilty,” Merlin says, winking at him as he walks into the room and takes a plate from Theo.

“Yeah well, you two lured me into it,” Theo says, accepting the kiss Merlin gives him with a smile. “You seduced me, both of you.”

Derek shakes his head, “Please, all I did was walk into the room without a shirt on and you were on me.”

“Exactly,” Theo says, pointing a figure at him as he takes his place at the table, “Seduction.”

“And what did I do?” Merlin asks, sitting down next to him and across from Derek.

Theo narrows his eyes, “You plastered yourself to my back and started kissing my neck while I was trying to make the toast. You know what that does to me”

Merlin just grins, “Oh that’s right.”

Derek watches the two of them with a smile. Sometimes he can’t believe he has this. 3 years ago he was afraid he’d have to choose between the two men he loves. He never counted on them getting to know each other and falling in love themselves. Except they did. Merlin moved in with them and took the spare room, which was Theo’s idea. He decided he didn’t want Derek to have to choose and his solution was for Merlin to just move in. Derek had been wary, thinking it might make things difficult. But it hadn’t.

Merlin and Theo got along surprisingly well. Derek remembers the first time he came home from work and found them curled up together on the couch, laughing about whatever TV show they were watching. They’d both turned to him and smiled. Theo had held out his hand and pulled him down onto the couch between them, both snuggling up into his side, their joined hand resting on his lap. That had been the first time he knew for sure this could work.

Derek remembers lying in bed between the two of them a few months after that, and being on the verge of sleep when Theo had shot up in bed, turning to Derek with wide eyes, “I’m in love with Merlin.”

Derek had smiled, feeling a warmth spread through his chest at the thought of his husband loving the first man he’d ever loved. Merlin had just groaned and sat up, rubbing his eyes tiredly, “I love you too, okay? But it’s 2 a.m. Go to sleep.”

He’d leaned over and placed a kiss to Theo’s lips before laying back down with his head on Derek’s chest. Theo had stared at him, his eyes wide. Then he’d smiled and done the same.

Now it’s a little over 2 years later and they’re here together sharing breakfast and casual conversation. He’s Derek but he’s also Arthur. Both of his lives have merged together seamlessly, something he never would have thought possible. But here he is, with the proof sitting on either side of him. As he looks around the table at Merlin and Theo he can’t help but feel grateful that he has the life he does. That he gets to be who he is and be with the two men that he loves. That no matter what happens they’re going to be Derek and Merlin and Theo.

**Author's Note:**

> Thanks for reading! Kudos/Comments make my day. ♥  
> [My tumblr](http://tabbytabbytabby.tumblr.com/)


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